Velocity vectors; arrow length

[paulb203]

Homework Statement

During which time interval does the dog have the greatest average velocity (see attached photo for diagram)

Relevant Equations

v=s/t

Does the v with the arrow underneath stand for velocity vector?

If so, does the length of the arrow indicate the magnitude of the velocity?

Is arrow length usually specific (x cm, or y mm, or whatever, indicating a specific magnitude, sometimes to scale)? Or is it usually relative (longer or shorter than another arrow, indicating simply greater or lesser magnitude). Nb; the arrows in the diagram seem very specific.

The first arrow goes from -4 to -2.5 a length of 1.5m. What does that indicate?

I know the displacement for that first interval is 5m therefore the velocity is 2.5m/s, which is why I’m wondering.

 

[Steve4Physics]

Homework Statement: During which time interval does the dog have the greatest average velocity (see attached photo for diagram)

Edit: here's your image - right way up though still blurry:

Does the v with the arrow underneath stand for velocity vector?

Yes.

If so, does the length of the arrow indicate the magnitude of the velocity?

Yes - if the diagram has been drawn to scale.

The arrows appear to be drawn to scale here - but it's risky to base your answer on this because velocity vectors on diagrams are not always drawn to scale. Or may not be drawn accurately. E.g. the same size arrow might be used for velocities of different magnitudes. It depends on the author and context. So don't assume they're to scale.

Is arrow length usually specific (x cm, or y mm, or whatever, indicating a specific magnitude, sometimes to scale)? Or is it usually relative (longer or shorter than another arrow, indicating simply greater or lesser magnitude). Nb; the arrows in the diagram seem very specific.

Here arrow-length represents speed (magnitude of velocity). There is no scale specified so you can't assume one. Arrow-length is probably intended to represent the instantanous speed at the start of the interval. It is drawn with a relative scale,

For example, for an accurately drawn diagram, if a two velocity vector arrows have lengths of 1cm and 2cm, they could represent speeds of 12m/s and 24m/s, or of 3km/h and 6km/h.

The first arrow goes from -4 to -2.5 a length of 1.5m. What does that indicate?

Nothing in itself. If a second arrow had length of (for example) 0.5cm, it would mean that the first speed is three times the second speed.

I know the displacement for that first interval is 5m therefore the velocity is 2.5m/s, which is why I’m wondering.

SorrNot sure what you mean. The first dot is at x=-4m. The second dot is at x=-1m. That's a total displacement for the first interval of 3m (in 1s). Average speed = 3m/s. Whoops - sorry, deleted.

Average velocity = displacement/time. Work out the three values and ignore the arrow-lengths.

Note: you'll get more/better answers if your diagram is the right way upand is clear!

EDIT. Various changes made.

 

[Steve4Physics]

It’s worth noting the question can (should?) be answered without any calculations.

Looking at the diagram, you can tell the dog (moving in a straight line) slows down and reaches a constant velocity. Can you see that?

All three intervals are 2s long, so which of them must have the greatest average velocity – the earliest, the one in the middle, or the latest?

 

[paulb203]

It’s worth noting the question can (should?) be answered without any calculations.

Looking at the diagram, you can tell the dog (moving in a straight line) slows down and reaches a constant velocity. Can you see that?

All three intervals are 2s long, so which of them must have the greatest average velocity – the earliest, the one in the middle, or the latest?

Thanks, Steve.
Really helpful as as ever.
Yes, I can see the dog slows down and reaches a constant v of 1m/s East.
And the earliest interval has the greatest average v (2.5m/s East).
It was the arrow lengths that confused me.